Valve With Removable Seat

ABSTRACT

A valve has a housing defining an inlet and an outlet and a cavity therebetween which receives a valve seat. The valve seat defines a slot which receives a gate. The valve seat is sealingly engaged with the housing, the gate sealingly engages the valve seat and is movable within the slot between an open and a closed position using an actuator. An opening in the housing provides access to the cavity. The valve seat may be removed from the housing through the opening by attaching the valve seat to the gate, thereby attaching the valve seat to the actuator, and withdrawing the gate from the housing using the actuator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority to U.S. ProvisionalApplication No. 61/820,202, filed May 7, 2013 and U.S. ProvisionalApplication No. 61/925,724 filed Jan. 10, 2014, both applications beinghereby incorporated by reference herein.

FIELD OF THE INVENTION

This invention concerns valves used in high wear environments.

BACKGROUND

In hydraulic fluid handling valve applications there are many differentfluid media to be considered, including, for example, water, variouschemicals, as well as thick, highly abrasive fluids commonly calledslurry. Slurries can have different levels of solid content as well asparticle sizes. Because slurries have a higher level of solids contentthan typical hydraulic fluids, they present unique operationaldifficulties such as increased wear rate of piping and valves in systemstransporting slurry.

Because of the increased wear rate on components caused by the slurry,it is typical for systems transporting slurry to have predeterminedmaintenance schedules for the replacement of worn parts such as seals,valve seats, and other components subject to wear. Such maintenanceusually requires shut down of the affected hydraulic lines and resultsin the loss of production.

Typical valves used in slurry applications are pinch and knife gatevalves which are designed specifically for the increased solid contentof the fluid and the resultant greater wear on components. In order toservice these types of valves it is necessary to remove either theentire valve or significant sections of pipe attached to the valve,resulting in increased down time of the production line and loss ofassociated revenue.

There is a clearly a need for components, such as valves, that can beserviced in a faster and more efficient manner to reduce production downtime and the concomitant loss of revenue.

SUMMARY

The invention concerns a valve. In one example embodiment, the valvecomprises a housing having an inlet and an outlet. A cavity ispositioned within the housing between the inlet and the outlet. A firstopening in the housing provides access to the cavity. A valve seat ispositioned within the cavity and sealingly engages the housing. Thevalve seat is insertable into and removable from the cavity through thefirst opening. A valve closing member is mounted within the valve seatand is movable relatively thereto between an open position and a closedposition sealingly engaging the valve seat. A first actuator is mountedon the housing and is engageable with the valve seat for removing thevalve seat and the valve closing member from the cavity through thefirst opening.

In another example, the valve may further comprise a second actuatormounted on the housing. The second actuator is engaged with the valveclosing member for moving the valve closing member between the open andthe closed positions. In a particular example, the valve closing membercomprises a body rotatably mounted within the valve seat, and the bodyis rotatably movable between the open and the closed positions. By wayof example, the valve closing member in this embodiment comprises adisk.

In a further example embodiment, the first actuator is engageable withthe valve closing member separately from the valve seat for moving thevalve closing member between the open and the closed positions. In aparticular example, the valve closing member comprises a gate slideablymounted within the valve seat, the gate being slidably movable betweenthe open and the closed positions. By way of further example, the gatemaybe pivotably attached to the first actuator or slidingly attached tothe first actuator.

By way of example, the cavity may be defined by first and second wallspositioned within the housing and oriented transversely to a flow axisextending from the inlet to the outlet. The first and second walls arein spaced relation to one another, each wall having a surface facingtoward and sealingly engaged with the valve seat. In a furtherembodiment, the valve seat comprises first and second sealing surfacespositioned in facing relation to one another and defining a slottherebetween. The valve closing member may comprise a gate slidablymovable within the slot between the open and closed positions. The gatein this example is oriented transversely to the flow axis and has firstand second oppositely disposed faces respectively sealingly engaging thefirst and second sealing surfaces of the valve seat.

By way of example, the valve may further comprise a strap attachable tothe gate for retaining the valve seat to the gate, thereby attaching thevalve seat to the actuator to facilitate removal thereof from thecavity. In an example embodiment, the first actuator comprises ajackscrew.

In a particular example embodiment, the housing comprises a firstsegment defining the first opening and a second segment attached to thefirst segment. The first and second segments are attached to one anotherend to end and define the inlet and the outlet and a flow axis extendingtherebetween. Additionally by way of example, each of the first andsecond segments comprises first and second lugs projecting outwardlyfrom opposite ends thereof. The lugs each have at least one hole forreceiving a fastener for attaching the segments to one another.

In a further example embodiment, each of the first and second segmentscomprises first and second arcuate projections positioned on oppositesides of the segments. The first and second arcuate projections surroundthe flow axis and extending radially there toward.

Further by way of example, each of the first and second segmentscomprises first and second grooves positioned on opposite sides of thesegments, each of the grooves facing the flow axis. First and secondgaskets are respectively positioned within the first and second grooves.In one example embodiment, the first and second grooves extend overinterfacing surfaces of the first and second lugs of the first andsecond segments. The first and second gaskets also extend along thefirst and second grooves in the lugs.

In an example embodiment, the inlet has an inner diameter and the valveseat defines an aperture having an inner diameter smaller than the innerdiameter of the inlet thereby defining a sealing surface facing theinlet. The sealing surface may comprise at least one projectionextending toward the inlet. Further by way of example, the outlet mayhave an inner diameter and the valve seat may define an aperture havingan inner diameter smaller than the inner diameter of the outlet therebydefining a sealing surface facing the outlet. In an example embodiment,the sealing surface comprises at least one projection extending towardthe outlet.

By way of example, the valve may further comprise a second opening inthe housing providing access to the cavity. In a particular exampleembodiment, the second opening is positioned opposite to the firstopening.

Another example further comprises a sealing body attachable to the valveseat. The sealing body is movable into the cavity through the secondopening upon removal of the valve seat through the first opening. In anexample embodiment, the sealing body comprises first and second sealingsurfaces oppositely disposed from one another and sealingly engageablewith the housing. In another example embodiment, the sealing bodycomprises a plurality of portions removably attachable to one another.For example, the sealing body may comprise a rectangular block.

By way of further example, the valve seat may comprise a plurality ofindependent piece parts attachable to one another. An additional examplemay further comprise a pivot hinge mounted on the housing. The firstactuator is mounted on the pivot hinge and is pivotably movable thereonrelatively to the housing in this example.

In another example embodiment, a valve comprises a housing having aninlet and an outlet. The housing comprises first and second segments.The first and second segments are attached to one another end to end anddefine the inlet and the outlet and a flow axis extending therebetween.A cavity is positioned within the housing between the inlet and theoutlet. A first opening is positioned in the first segment, and a secondopening is positioned in the second segment. The first and secondopenings provide access to the cavity. A valve seat is positioned withinthe cavity and sealingly engages the housing. The valve seat isinsertable into and removable from the cavity through one of the firstand second openings. A valve closing member is mounted within the valveseat and is movable relatively thereto between an open position and aclosed position sealingly engaging the valve seat. A first actuator ismounted on the housing and engageable with the valve seat for insertingand removing the valve seat and the valve closing member into and fromthe cavity through one of the first and second openings.

In a particular example, each of the first and second segments comprisesfirst and second lugs projecting outwardly from opposite ends thereof,the lugs each having at least one hole for receiving a fastener forattaching the segments to one another. Further by way of example, eachof the first and second segments comprises first and second arcuateprojections positioned on opposite sides of the segments. The first andsecond arcuate projections surround the flow axis and extending radiallythere toward.

In an example embodiment, each of the first and second segmentscomprises first and second grooves positioned on opposite sides of thesegments. Each of the grooves faces the flow axis in this example. Firstand second gaskets are respectively positioned within the first andsecond grooves. In a particular example, the second opening ispositioned opposite to the first opening. By way of example, the gatemay be pivotably attached to the first actuator. Another exampleembodiment further comprises a second actuator mounted on the housing.The second actuator is engaged with the valve closing member for movingthe valve closing member between the open and the closed positions. Byway of example, the valve closing member comprises a body rotatablymounted within the valve seat, the body being rotatably movable betweenthe open and the closed positions. In a particular example, the valveclosing member comprises a disk.

In an example embodiment, the first actuator is engageable with thevalve closing member separately from the valve seat for moving the valveclosing member between the open and the closed positions. By way ofexample, the valve closing member comprises a gate slideably mountedwithin the valve seat. The gate is slidably movable between the open andthe closed positions.

An example embodiment further comprises a sealing body attachable to thevalve seat. The sealing body is movable into the cavity through thesecond opening upon removal of the valve seat through the first opening.In a particular example, the sealing body comprises first and secondsealing surfaces oppositely disposed from one another and sealinglyengageable with the housing. In a further example, the sealing bodycomprises a plurality of portions removably attachable to one another.By way of example, the sealing body may comprise a rectangular block.

In another example embodiment, the valve seat comprises a plurality ofindependent piece parts attachable to one another.

By way of example, a pivot hinge is mounted on the housing. The firstactuator is mounted on the pivot hinge and is pivotably movable thereonrelatively to the housing. Another example embodiment of a valvecomprises a housing having an inlet and an outlet. The housing comprisesfirst and second segments. The first and second segments are attached toone another end to end and defining the inlet and the outlet and a flowaxis extending therebetween. In this example a cavity is positionedwithin the housing between the inlet and the outlet. A first opening ispositioned in the first segment and providing access to the cavity. Avalve seat is positioned within the cavity and sealingly engages thehousing. The valve seat comprises a first piece part positioned withinthe first segment and a second piece part positioned within the secondsegment. The first piece part of the valve seat is insertable into andremovable from the cavity through the first opening. A valve closingmember is mounted within the valve seat and movable relatively theretobetween an open position, and a closed position sealingly engaging thevalve seat. A first actuator is mounted on the housing and engageablewith the first piece part of the valve seat for inserting and removingthe first piece part of the valve seat and the valve closing member intoand from the cavity through the first opening.

In one example embodiment, the cavity is defined by first and secondwalls positioned within the housing and oriented transversely to a flowaxis extending from the inlet to the outlet. The first and second wallsare in spaced relation to one another. Each wall has a surface facingtoward and sealingly engaged with the valve seat.

In an example, the first piece part of the valve seat comprises firstand second sealing surfaces positioned in facing relation to one anotherand defining a slot therebetween. The valve closing member comprises agate slidably movable within the slot between the open and closedpositions in an example embodiment. The gate is oriented transversely tothe flow axis and has first and second oppositely disposed facesrespectively sealingly engaging the first and second sealing surfaces ofthe first piece part of the valve seat.

An example embodiment may further comprise a strap attachable to saidgate for retaining said valve seat to said gate, thereby attaching thevalve seat to the actuator to facilitate removal thereof from thecavity.

The invention also encompasses a method of removing a valve seat from avalve. The valve has a closing member engaging the valve seat. Anactuator engages the valve closing member. An example method comprises:

-   -   attaching the valve seat to the valve closing member;    -   drawing both the valve seat and the valve closing member from        the valve using the actuator engaging the valve closing member.

A method of replacing a valve seat is also contemplated. The valve has aclosing member engagable with the valve seat and an actuator engagingthe valve closing member. An example method comprises:

-   -   engaging the valve seat with the closing member;    -   moving both the valve seat and the valve closing member into the        valve using the actuator engaging the valve closing member.

The invention further encompasses a method of replacing a valve seat ina valve using a blocking body. In a particular example, the methodcomprises:

-   -   attaching the blocking body to the valve seat;    -   drawing the valve seat from the valve while drawing the blocking        body into the valve;    -   detaching the valve seat from the blocking body;    -   attaching a new valve seat to the blocking body;    -   inserting the new valve seat into the valve while forcing the        blocking body from the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an isometric view of an example valve embodiment accordingto the invention;

FIGS. 2 and 3 show longitudinal sectional views of a portion of thevalve shown in FIG. 1;

FIGS. 2A and 2B show portions of the valve of FIG. 1 in isolation;

FIG. 4 shows a cross sectional view taken at lines 4-4 of FIG. 2;

FIGS. 5 and 6 are isometric views showing example embodiments ofportions of valves according to the invention;

FIGS. 7-9 are partial sectional isometric views illustrating an examplemethod of replacing a valve seat according to the invention;

FIG. 10 is a partial isometric sectional view of an example embodimentof a valve seat according to the invention; and

FIG. 11 is a partial isometric sectional view of an example embodimentof a valve seat and valve closing member according to the invention.

DETAILED DESCRIPTION

FIG. 1 shows an example embodiment of a valve 10 according to theinvention. Valve 10 comprises a housing 12 having an inlet 14 and anoutlet 16. Housing 12 may be formed from a metal such as ductile iron,cast iron or steel, composites such as fiberglass, and polymers such asPVC (polyvinylchloride). Housing 12 comprises a first segment 18 and asecond segment 20 attached to one another end to end and thereby definethe inlet 14, the outlet 16, and a flow axis 22 extending between them.In this example embodiment the segments 18 and 20 have projecting lugs24 each having one or more aligned holes 26 that receive fasteners 28for attaching the segments to one another. When used to connect groovedpipe elements (see FIG. 2) the segments will have arcuate projections 30(also known as “keys”) positioned on opposite sides 32 and 34 of thesegments 18 and 20. The arcuate projections 30 surround and face theflow axis 22 and extend radially toward it, allowing them to engagecircumferential grooves within the pipe elements and provide mechanicalengagement to retain the pipe elements to the valve 10.

As shown in FIG. 2, a cavity 36 is positioned within the housing 12between the inlet 14 and the outlet 16. A first opening 38 within thefirst segment 18 provides access to cavity 36. A valve seat 40 ispositioned within the cavity 36. Valve seat 40 may be advantageouslyformed from a resilient, flexible material such as a rubber compound orurethane. The valve seat is insertable into the cavity 36 through theopening 38 and sealingly engages the housing. In this exampleembodiment, sealing engagement between seat 40 and housing 12 iseffected through contact between oppositely facing surfaces 42 and 44 ofthe valve seat respectively engaging first and second housing walls 46and 48. Walls 46 and 48 are oriented transversely to the flow axis 22and are in spaced relation from one another to define the cavity 36.Upon insertion into cavity 36, the valve seat 40 is compressed betweenthe walls 46 and 48 to effect a seal at the engaging surfaces. Note thatit may be advantageous to position projections 50 on the surfaces 42 and44 to ensure a uniform compression, and hence, a fluid tight seal,between valve seat 40 and housing 12.

Inlet 14 and outlet 16 each have respective inner diameters 14 a and 16a which are substantially aligned with an aperture 52 defined by thevalve seat. Together the inlet 14, outlet 16 and aperture 52 define theflow axis 22 through the valve 10. In the example shown, the aperture 52of the valve seat 40 has an inner diameter 52 a less than the respectiveinner diameters 14 a and 16 a of the inlet 14 and the outlet 16. Thisdifference in diameters creates two axial sealing surfaces, sealingsurface 54, which faces inlet 14, and sealing surface 56, which facesoutlet 16. As shown in FIGS. 2 and 3, axial sealing surfaces 54 and 56engage the ends of pipe elements 58 and 60 joined by the valve 10.Compression between the ends of pipe elements 58 and 60 and the axialsealing surfaces 54 and 56 is provided by the positions of arcuateprojections 30 and the pipe element's circumferential grooves 62. Axialprojections 64 positioned respectively on the sealing surfaces 54 and 56and extending respectively toward the inlet 14 and outlet 16 may be usedto ensure a uniform seal between the pipe elements 58 and 60 and theseat 40. Additional or alternate sealing between the pipe elements 58and 60 and the housing may be effected by gaskets 66 positioned inrespective grooves 68 and 70 in the segments 18 and 20. Grooves 68 and70 are positioned on opposite sides 32 and 34 of the segments and facethe flow axis 22. Gaskets 66 engage the segments and the pipe elementsto effect a fluid tight seal therebetween. As shown in FIGS. 2A, 2B and4, grooves 68 and 70 and gaskets 66 may also extend along theinterfacing surfaces 24 a and 24 b of lugs 24. This seal configurationis shown in FIG. 2B in isolation to demonstrate how the seals 66 engageone another and form a complete sealing boundary to eliminate anypotential leak paths between segments 18 and 20.

As shown in FIG. 3, valve seat 40 comprises first and second sealingsurfaces 72 and 74 arranged spaced apart from one another in facingrelation to define a slot 76. A valve closing member in the form of agate 78 is slidably movable within slot 76 between a closed position(shown in FIG. 2) wherein gate 78 sealingly engages the sealing surfaces72 and 74 and obstructs flow through the aperture 52, and an openposition (shown in FIG. 3) which permits flow between the inlet 14 andoutlet 16. Gate 78 may be made of metal, for example, steel, as well ascomposites such as fiberglass, as well as polymers such as HDPE (highdensity polyethylene). Gate 78 is in compressive engagement with sealingsurfaces 72 and 74 when in the closed position. To ensure a uniform sealbetween the gate 78 and the valve seat 40, it is advantageous toposition circumferential projections 80 on the surfaces 72 and 74.

Movement of gate 78 is effected by an actuator, in this example a risingstem jackscrew 82 (see FIG. 1) mounted on the first segment 18 of thehousing 12. Other types of actuators, such as pneumatic actuators,hydraulic actuators and electrical actuators, are also feasible. Theshaft of jackscrew 82 engages the gate 78 separately from the valve seat40, and rotation of the jackscrew's actuation wheel moves the jackscrewshaft, which moves the gate within the slot 76 of valve seat 40 betweenthe open and closed positions as shown in FIGS. 2 and 3. The seat 40 isadvantageously held within the cavity 36 by a retainer plate 84removably fastened to the housing 12, otherwise, the considerablefriction between the gate 78 and the sealing surfaces 72 and 74 (seeFIG. 3) might remove the valve seat 40 from the cavity when the gate 78is drawn away from the housing 12. However, the actuator (jackscrew 82)may be engaged with both the valve closing member (gate 78) and thevalve seat 40 to intentionally remove both the gate and the valve seatfrom the cavity 36. This permits ready replacement of a worn valve seatwithout removing the valve 10 from the pipe elements 58 and 60. Seatreplacement may be effected by removing the retainer plate 84 to permitthe valve seat 40 to move through the opening 38 in the segment 18.Actuation of the jackscrew 82 to withdraw the gate 78 from the slot 76may, instead, remove the valve seat 40 from cavity 36 provided that thefriction between the gate and the valve seat is greater than thefriction between the valve seat and the housing 12. However, it isadvantageous to provide mechanical engagement between the actuator 82and the valve seat 40 to ensure removal as desired. To this end, asshown in FIGS. 1 and 4, a strap 86 is positioned surrounding the valveseat 40 within the cavity 36. Strap 86 may be attached to the gate 78using, for example, bolts 88 to provide mechanical engagement permittingthe valve seat 40 to be withdrawn from cavity 36 with the gate 78 usingthe actuator. As shown in FIG. 5, to further facilitate valve seatreplacement, the actuator, jackscrew 82, may be mounted on a pivot hinge90 to permit pivoting motion of the gate 78 and valve seat 40 for readyaccess. The worn valve seat 40 may then be removed from the gate 78 byunbolting strap 86, sliding the worn valve seat from the gate, sliding anew valve seat onto the gate, bolting the strap 86 to the gate, rotatingthe jackscrew 82 on pivot hinge 90 to align the gate and valve seat withopening 38 (see FIGS. 2 and 3), and then using the jackscrew to forcethe new valve seat into the cavity 36. Once the valve seat is properlyseated within the cavity 36 the bolts 88 may be removed and the retainerplate 84 may be reattached to the segment 18. In another embodiment,shown in FIG. 6, the gate 78 may be pivotably attached to the actuator,in this example, jackscrew 82. Still another embodiment is shown in FIG.1, wherein gate 78 is slidingly attached to the actuator (jackscrew 82)using a “Tee” coupling 92 which permits both the gate 78 and valve seat40 to be removed as an assembly when they are drawn from the cavity 36.The assembly slides along an axis perpendicular to flow axis 22 topermit rapid and convenient replacement of a worn valve seat.

In another valve embodiment 94, shown in FIG. 7, replacement of a wornvalve seat 40 is further facilitated through the use of a sealing body96. Sealing body 96 permits replacement of the valve seat 40 withoutinterrupting fluid flow to the valve 94. Valve 94 has a second opening98 positioned in the second segment 20 opposite to the first opening 38.The second opening 98 provides access to cavity 36, and allows thesealing body 96 to be removably attached to the valve seat 40. In thisexample embodiment, the sealing body 96 comprises a rectangular block100 having oppositely disposed sealing surfaces 102 and 104. As shown inFIG. 8, when the sealing body 96 is temporarily attached to the valveseat 40, and the valve seat is drawn out of the cavity 36 by theactuator 82 through opening 38 in the first segment 18, the sealing body98 is drawn into the cavity 36 through the second opening 98 in thesecond segment 20. Sealing surfaces 102 and 104 of the block 100sealingly engage the housing 12, namely walls 46 and 48, thereby closingthe valve 94. The valve seat 40 is then released from the sealing body96, and may be replaced as described above, with the additional step ofattaching the valve seat 40 to the sealing body 96. When the new valveseat 40 is inserted into the cavity 36 through opening 38 in the segment18 the sealing body 96 (block 100 in this example) is forced out of thecavity through the opening 98 in the segment 20. The sealing body maythen be disengaged from the new valve seat 40. Temporary attachment ofthe valve seat 40 to the sealing body 98 may be effected throughfriction of contacting surfaces of interengaging parts, aligned holesand pins, spring biased detents, or dovetail joints for example. It mayalso be advantageous if the sealing body 96 comprises a plurality ofinterlocking portions 106 removably attachable to one another as shownin FIG. 9. This allows the sealing body to be assembled and drawn intothe cavity 36 a portion at a time, and is useful when space is notavailable to accommodate a full sized block 100 for example. Portions106 may be temporarily joined to one another using dovetail joints asshown, or using friction of contacting surfaces of interengaging parts,spring biased detents, and aligned holes and pins to cite a fewexamples.

As shown in FIG. 10, a valve seat 108 can be formed from a plurality ofindependent piece parts that cooperate with one another. In thisexample, valve seat 108 comprises first and second piece parts 110 and112 positionable within the cavity 36 of example valve embodiments 10instead of seat 40 (see FIG. 2) and valve embodiment 94 (see FIG. 7).The first and second piece parts 110, 112 comprise first and secondsealing surfaces 114 and 116 oppositely disposed from one another andsealingly engageable with the housing 12. The first and second pieceparts 110 and 112 further comprise sealing surfaces 118 and 120positioned in facing relation to one another and defining a slot 122therebetween. The slot receives the gate 78 in sealing relation.

Although the example embodiments shown pertain to gate valves, theinvention is also applicable to other types of valves. As shown in FIG.11, a body 124 is rotatably mounted within a valve seat 126, the bodybeing rotatable about axis 128 between an open position, and a closedposition sealingly engaging the valve seat 126. In this example thevalve closing member comprises a disk 130 characteristic of thewell-known “butterfly” valve. Like valve seat 40 described above, thevalve seat 126 can be inserted into and removed from the cavity 36 of ahousing 12 (see FIG. 1) through an opening 38 (see FIG. 2) as describedabove when the disk 130 is in the closed position. Because the valveclosing member is actuated by rotation about axis 128, the actuator(jackscrew 82) which is used to draw the valve seat 126 from the housingcannot also be used to actuate the valve. Therefore, a second actuator(hand lever 132 for example) is mounted on the housing to rotate thedisk 130. Although a simple hand lever is shown, the second actuatorcould be a motorized gear train, or other form of power actuation.

What is claimed is:
 1. A valve, comprising: a housing having an inletand an outlet; a cavity positioned within said housing between saidinlet and said outlet, a first opening in said housing providing accessto said cavity; a valve seat positioned within said cavity and sealinglyengaging said housing, said valve seat being insertable into andremovable from said cavity through said first opening; a valve closingmember mounted within said valve seat and movable relatively theretobetween an open position and a closed position sealingly engaging saidvalve seat; a first actuator mounted on said housing and engageable withsaid valve seat for removing said valve seat and said valve closingmember from said cavity through said first opening.
 2. The valveaccording to claim 1, further comprising a second actuator mounted onsaid housing, said second actuator being engaged with said valve closingmember for moving said valve closing member between said open and saidclosed positions.
 3. The valve according to claim 2, wherein said valveclosing member comprises a body rotatably mounted within said valveseat, said body being rotatably movable between said open and saidclosed positions.
 4. The valve according to claim 3, wherein said valveclosing member comprises a disk.
 5. The valve according to claim 1,wherein said first actuator is engageable with said valve closing memberseparately from said valve seat for moving said valve closing memberbetween said open and said closed positions.
 6. The valve according toclaim 5, wherein said valve closing member comprises a gate slideablymounted within said valve seat, said gate being slidably movable betweensaid open and said closed positions.
 7. The valve according to claim 6,wherein said gate is pivotably attached to said first actuator.
 8. Thevalve according to claim 6, wherein said gate is slidingly attached tosaid first actuator.
 9. The valve according to claim 1, wherein saidcavity is defined by first and second walls positioned within saidhousing and oriented transversely to a flow axis extending from saidinlet to said outlet, said first and second walls being in spacedrelation to one another, each said wall having a surface facing towardand sealingly engaged with said valve seat.
 10. The valve according toclaim 9, wherein: said valve seat comprises first and second sealingsurfaces positioned in facing relation to one another and defining aslot therebetween; said valve closing member comprises a gate slidablymovable within said slot between said open and closed positions, saidgate being oriented transversely to said flow axis and having first andsecond oppositely disposed faces respectively sealingly engaging saidfirst and second sealing surfaces of said valve seat.
 11. The valveaccording to claim 10, further comprise a strap attachable to said gatefor retaining said valve seat to said gate, thereby attaching said valveseat to said actuator to facilitate removal thereof from said cavity.12. The valve according to claim 11, wherein said first actuatorcomprises a jackscrew.
 13. The valve according to claim 1, wherein saidhousing comprises a first segment defining said first opening and asecond segment attached to said first segment, said first and secondsegments being attached to one another end to end and defining saidinlet and said outlet and a flow axis extending therebetween.
 14. Thevalve according to claim 13, wherein each of said first and secondsegments comprises first and second arcuate projections positioned onopposite sides of said segments, said first and second arcuateprojections surrounding said flow axis and extending radially theretoward.
 15. The valve according to claim 13, wherein each of said firstand second segments comprises first and second lugs projecting outwardlyfrom opposite ends thereof, said lugs each having at least one hole forreceiving a fastener for attaching said segments to one another.
 16. Thevalve according to claim 15, wherein each of said first and secondsegments comprises: first and second grooves positioned on oppositesides of said segments, each of said grooves facing said flow axis;first and second gaskets respectively positioned within said first andsecond grooves.
 17. The valve according to claim 16, wherein said firstand second grooves extend over interfacing surfaces of said first andsecond lugs of said first and second segments, said first and secondgaskets extending along said first and second grooves in said first andsecond lugs.
 18. The valve according to claim 13, wherein: said inlethas an inner diameter; said valve seat defines an aperture having aninner diameter smaller than said inner diameter of said inlet therebydefining a sealing surface facing said inlet.
 19. The valve according toclaim 18, wherein said sealing surface comprises at least one projectionextending toward said inlet.
 20. The valve according to claim 13,wherein: said outlet has an inner diameter; said valve seat defines anaperture having an inner diameter smaller than said inner diameter ofsaid outlet thereby defining a sealing surface facing said outlet. 21.The valve according to claim 20, wherein said sealing surface comprisesat least one projection extending toward said outlet.
 22. The valveaccording to claim 1, further comprising: a second opening in saidhousing providing access to said cavity.
 23. The valve according toclaim 22, wherein said second opening is positioned opposite to saidfirst opening.
 24. The valve according to claim 22, further comprising asealing body attachable to said valve seat, said sealing body beingmovable into said cavity through said second opening upon removal ofsaid valve seat through said first opening.
 25. The valve according toclaim 22, wherein said sealing body comprises: first and second sealingsurfaces oppositely disposed from one another and sealingly engageablewith said housing.
 26. The valve according to claim 24, wherein saidsealing body comprises a plurality of portions removably attachable toone another.
 27. The valve according to claim 24, wherein said sealingbody comprises a rectangular block.
 28. The valve according to claim 1,wherein said valve seat comprises a plurality of independent piece partsattachable to one another.
 29. The valve according to claim 1, furthercomprising: a pivot hinge mounted on said housing, said first actuatorbeing mounted on said pivot hinge and being pivotably movable thereonrelatively to said housing.
 30. A valve, comprising: a housing having aninlet and an outlet, said housing comprising first and second segments,said first and second segments being attached to one another end to endand defining said inlet and said outlet and a flow axis extendingtherebetween; a cavity positioned within said housing between said inletand said outlet, a first opening being positioned in said first segment,and a second opening being positioned in said second segment, said firstand second openings providing access to said cavity; a valve seatpositioned within said cavity and sealingly engaging said housing, saidvalve seat being insertable into and removable from said cavity throughone of said first and second openings; a valve closing member mountedwithin said valve seat and movable relatively thereto between an openposition and a closed position sealingly engaging said valve seat; and afirst actuator mounted on said housing and engageable with said valveseat for inserting and removing said valve seat and said valve closingmember into and from said cavity through one of said first and secondopenings.
 31. The valve according to claim 30, wherein each of saidfirst and second segments comprises first and second lugs projectingoutwardly from opposite ends thereof, said lugs each having at least onehole for receiving a fastener for attaching said segments to oneanother.
 32. The valve according to claim 30, wherein each of said firstand second segments comprises first and second arcuate projectionspositioned on opposite sides of said segments, said first and secondarcuate projections surrounding said flow axis and extending radiallythere toward.
 33. The valve according to claim 30, wherein each of saidfirst and second segments comprises: first and second grooves positionedon opposite sides of said segments, each of said grooves facing saidflow axis; first and second gaskets respectively positioned within saidfirst and second grooves.
 34. The valve according to claim 30, whereinsaid second opening is positioned opposite to said first opening. 35.The valve according to claim 30, wherein said gate is pivotably attachedto said first actuator.
 36. The valve according to claim 30, furthercomprising a second actuator mounted on said housing, said secondactuator being engaged with said valve closing member for moving saidvalve closing member between said open and said closed positions. 37.The valve according to claim 36, wherein said valve closing membercomprises a body rotatably mounted within said valve seat, said bodybeing rotatably movable between said open and said closed positions. 38.The valve according to claim 37, wherein said valve closing membercomprises a disk.
 39. The valve according to claim 30, wherein saidfirst actuator is engageable with said valve closing member separatelyfrom said valve seat for moving said valve closing member between saidopen and said closed positions.
 40. The valve according to claim 39,wherein said valve closing member comprises a gate slideably mountedwithin said valve seat, said gate being slidably movable between saidopen and said closed positions.
 41. The valve according to claim 30,further comprising a sealing body attachable to said valve seat, saidsealing body being movable into said cavity through said second openingupon removal of said valve seat through said first opening.
 42. Thevalve according to claim 41, wherein said sealing body comprises: firstand second sealing surfaces oppositely disposed from one another andsealingly engageable with said housing.
 43. The valve according to claim41, wherein said sealing body comprises a plurality of portionsremovably attachable to one another.
 44. The valve according to claim41, wherein said sealing body comprises a rectangular block.
 45. Thevalve according to claim 30, wherein said valve seat comprises aplurality of independent piece parts attachable to one another.
 46. Thevalve according to claim 30, further comprising: a pivot hinge mountedon said housing, said first actuator being mounted on said pivot hingeand being pivotably movable thereon relatively to said housing.
 47. Avalve, comprising: a housing having an inlet and an outlet, said housingcomprising first and second segments, said first and second segmentsbeing attached to one another end to end and defining said inlet andsaid outlet and a flow axis extending therebetween; a cavity positionedwithin said housing between said inlet and said outlet, a first openingbeing positioned in said first segment and providing access to saidcavity; a valve seat positioned within said cavity and sealinglyengaging said housing, said valve seat comprising a first piece partpositioned within said first segment and a second piece part positionedwithin said second segment, said first piece part of said valve seatbeing insertable into and removable from said cavity through said firstopening; a valve closing member mounted within said valve seat andmovable relatively thereto between an open position, and a closedposition sealingly engaging said valve seat; and a first actuatormounted on said housing and engageable with said first piece part ofsaid valve seat for inserting and removing said first piece part of saidvalve seat and said valve closing member into and from said cavitythrough said first opening.
 48. The valve according to claim 47, whereinsaid cavity is defined by first and second walls positioned within saidhousing and oriented transversely to a flow axis extending from saidinlet to said outlet, said first and second walls being in spacedrelation to one another, each said wall having a surface facing towardand sealingly engaged with said valve seat.
 49. The valve according toclaim 48, wherein: said first piece part of said valve seat comprisesfirst and second sealing surfaces positioned in facing relation to oneanother and defining a slot therebetween; said valve closing membercomprises a gate slidably movable within said slot between said open andclosed positions, said gate being oriented transversely to said flowaxis and having first and second oppositely disposed faces respectivelysealingly engaging said first and second sealing surfaces of said firstpiece part of said valve seat.
 50. The valve according to claim 49,further comprise a strap attachable to said gate for retaining saidvalve seat to said gate, thereby attaching said valve seat to saidactuator to facilitate removal thereof from said cavity.
 51. The valveaccording to claim 47, wherein each of said first and second segmentscomprises first and second lugs projecting outwardly from opposite endsthereof, said lugs each having at least one hole for receiving afastener for attaching said segments to one another.
 52. The valveaccording to claim 47, wherein each of said first and second segmentscomprises first and second arcuate projections positioned on oppositesides of said segments, said first and second arcuate projectionssurrounding said flow axis and extending radially there toward.
 53. Thevalve according to claim 47, wherein each of said first and secondsegments comprises: first and second grooves positioned on oppositesides of said segments, each of said grooves facing said flow axis;first and second gaskets respectively positioned within said first andsecond grooves.
 54. The valve according to claim 47, wherein: said inlethas an inner diameter; said first piece part of said valve seat definesan aperture having an inner diameter smaller than said inner diameter ofsaid inlet thereby defining a sealing surface facing said inlet.
 55. Thevalve according to claim 54, wherein said sealing surface comprises atleast one projection extending toward said inlet.
 56. The valveaccording to claim 47, wherein: said outlet has an inner diameter; saidfirst piece part of said valve seat defines an aperture having an innerdiameter smaller than said inner diameter of said outlet therebydefining a sealing surface facing said outlet.
 57. The valve accordingto claim 56, wherein said sealing surface comprises at least oneprojection extending toward said outlet.
 58. The valve according toclaim 47, wherein said first actuator comprises a jackscrew.
 59. Amethod of removing a valve seat from a valve, said valve having aclosing member engaging said valve seat and an actuator engaging saidvalve closing member, said method comprising: attaching said valve seatto said valve closing member; drawing both said valve seat and saidvalve closing member from said valve using said actuator engaging saidvalve closing member.
 60. A method of replacing a valve seat in a valve,said valve having a closing member engagable with said valve seat and anactuator engaging said valve closing member, said method comprising:engaging said valve seat with said closing member; moving both saidvalve seat and said valve closing member into said valve using saidactuator engaging said valve closing member.
 61. A method of replacing avalve seat in a valve using a blocking body, said method comprising:attaching said blocking body to said valve seat; drawing said valve seatfrom said valve while drawing said blocking body into said valve;detaching said valve seat from said blocking body; attaching a new valveseat to said blocking body; inserting said new valve seat into saidvalve while forcing said blocking body from said valve.